Rotary table device

Abstract

A rotary table device for a machine tool includes a main shaft that is rotatably supported in an insertion hole formed in a frame; a table that is secured to an end side of the main shaft, and on which a workpiece, serving as an object to be processed, is mounted; a clamp piston that is provided so as to be movable in an axial direction of the main shaft in the insertion hole; and a bearing that is provided between the table and the frame, and that directly supports the table with respect to the frame. The main shaft has a clamp surface facing the table. A pressure chamber is defined by the frame and the clamp piston. When an operating fluid is supplied to the pressure chamber, the clamp piston is caused to press-contact the clamp surface, so that the table is brought into a clamped state.

What is claimed is: 
     
       1. A rotary table device for a machine tool comprising:
 a main shaft that is rotatably supported with respect to a frame by a first bearing in an insertion hole formed in the frame; 
 a table that is secured to an end side of the main shaft, and on which a workpiece, which serves as an object to be processed, is mounted; and
 a clamp piston that is provided so as to be movable in an axial direction of the main shaft in the insertion hole, 
 
 wherein the main shaft has a clamp surface that faces the table, 
 wherein a pressure chamber is defined by the frame and the clamp piston, 
 wherein the table is brought into a clamped state by friction force that is generated between the clamp piston and the clamp surface by causing the clamp piston to press-contact the clamp surface when an operating fluid is supplied to the pressure chamber, 
 wherein the rotary table device further comprises a second bearing that is provided separately from the first bearing, the second bearing being provided between the table and the frame so as to contact the table and the frame, and being provided so as to directly support the table with respect to the frame, and 
 wherein at least part of the second bearing is provided so as to be positioned within a range of existence of the pressure chamber in a radial direction of the main shaft. 
 
     
     
       2. The rotary table device according to  claim 1 , wherein the frame includes a body portion that is mounted on the machine tool and a cylinder portion that is secured to the body portion so as to be positioned between the table and the clamp piston in the axial direction in the body portion,
 wherein at least part of the pressure chamber is defined by the clamp piston and the cylinder portion, and 
 wherein the second bearing is provided between the table and the cylinder portion, and the table is supported by the cylinder portion of the frame with the second bearing interposed between the table and the cylinder portion. 
 
     
     
       3. A rotary table device for a machine tool comprising:
 a main shaft that is rotatably supported with respect to a frame by a first bearing in an insertion hole formed in the frame; 
 a table that is secured to an end side of the main shaft, and on which a workpiece, which serves as an object to be processed, is mounted; and
 a clamp piston that is provided so as to be movable in an axial direction of the main shaft in the insertion hole, 
 
 wherein the main shaft has a clamp surface that faces the table, 
 wherein a pressure chamber is defined by the frame and the clamp piston, 
 wherein the table is brought into a clamped state by friction force that is generated between the clamp piston and the clamp surface by causing the clamp piston to press-contact the clamp surface when an operating fluid is supplied to the pressure chamber, 
 wherein the rotary table device further comprises a second bearing that is provided separately from the first bearing, the second bearing being provided between the table and the frame and in direct contact with the table and the frame, the second bearing directly supporting the table with respect to the frame, and 
 wherein at least part of the second bearing is provided so as to be positioned within a range of existence of the pressure chamber in a radial direction of the main shaft.